Facebook’s vice president of Marketplace, Deb Liu believes the future of commerce is social.

There’s a saying in business school that entrepreneurs should eat their own dog food. Deb Liu takes that principle to the next level.

Facebook’s vice president of Marketplace sold her washer dryer on the platform last November. The other day, she picked up some cast-iron skillets from a local seller. “They’re very expensive and I got a great deal,” she says proudly.

As a high-ranking executive at Facebook Liu could have easily afforded the skillets brand new, but once she’s revealed what she does to people who she meets through Marketplace, she’ll also try and find out what they think of the site. “A lot of them talk about how it’s made it easier for them buy and sell,” she says from a conference room at Facebook’s headquarters in Menlo Park.

So enthusiastic is Liu about using Marketplace that she’s encouraged her three kids to sell their toys on the site too, using an Excel spreadsheet with fields for MSRP (the manufacturer’s suggested retail price), cost, sale price and profit. On Saturdays her three children take photographs of their old Frozen dolls and games and fill out the spreadsheet, while Liu reaches out to buyers to arrange pickup.

Liu’s son fills out a spreadsheet listing toys he’s selling on Facebook Marketplace.

“They’re excited about seeing things on Marketplace,” says Liu, who also helps them calculate their margins for each sale.

Launched in October 2016, Marketplace is less than a year-and-a-half old but already holds a prominent place on Facebook’s main site. It’s the third tab down from the top left, just under Newsfeed and Messenger; on the app, it took the position previously held by Messenger.

Around 550 million people across 36 countries use the platform each month and searches on Marketplace tripled over the course of 2017, a spokesperson for Facebook says. It has no plans to charge fees to sellers now or in the future.

Like the rest of the site, money will come from advertising. Liu’s team is testing ads but “it’ll be a while” before they roll that out to all users she says, not wanting to elaborate further.

Marketplace recently launched a section for car sales and apartment rentals and is gearing up to host small businesses too. But the business has yet to contribute the level of revenue that her previous stint at Facebook did, when she ran app install advertising. That quickly became one of Facebook’s fastest-growing and lucrative businesses.

Marketplace is an extension of that role for Liu, and something she’s been heading towards through a career that spanned roles at eBay and PayPal. “I gave up all my other projects to focus on this,” she says referring to her more recent responsibilities at Facebook. “I’ve always been extremely passionate about commerce, and how commerce connects people.”

Marketplace poses an obvious challenge to the likes of Craigslist and eBay, which has been dealing with a slide in its own marketplace sales. As a social media site first and foremost, you also can see far more about a buyer or seller’s identity on Facebook than you can on Craigslist. And while eBay benefits from nearly two decades of experience in auction selling, Facebook vastly outranks it in users: eBay had around 170 million active users in the third quarter of 2017, while Facebook had more than 2 billion.

But Marketplace probably wouldn’t be here if it wasn’t for Liu.

She held the first conversations with Mark Zuckerberg and Sheryl Sandberg three years ago about building a section of Facebook where people could buy and sell things. In true move-fast-break-things style, Liu put strategy to the side initially to watch how people were already bartering for goods with Facebook Groups.

While there were some questionable use-cases for selling items on the site, mothers in particular were using Groups to sell toys and baby clothes, and Liu was seeing it firsthand. “I’m personally part of a number of these groups,” she says.

She tasked a small team of engineers to reach out to several groups and offer to restructure them, so that the admins could upload products and separate data like price, descriptions and location.

That made it easier to search for the items, and for Liu’s team to see what people were buying and selling to eventually start recommending products. They worked with Groups in this way for a year and a half, proving out the concept before building a separate platform.

If Zuckerberg was wary of moving into e-commerce he had good reason. Facebook first introduced a feature called Marketplace in 2007, where users could post classified ads for goods and job vacancies, but it never picked up traction and was shut down in 2014.

Not only is the new Marketplace growing, though, it has the potential to shift people’s perceptions of Facebook away from its notoriously distracting reputation. “We talked to a lot of [Facebook users] and they said this is making Facebook more useful for me,” says Liu.

“Useful” isn’t a word you might normally associate with Zuckerberg’s social media time-suck, but particularly for those in emerging market, it can become a livelihood. Many small businesses in countries like Brazil already make a large proportion of their sales through Instagram and WhatsApp.

Down the line, Liu wants to increase Marketplace’s utility by incorporating machine-learning and computer vision. Her team is working on making it possible for Facebook to recognize that you’re pointing your camera at child’s tricycle, for instance, so that you don’t have to type out a title or description.

Facebook is already using the data being uploaded onto Marketplace to train its visual search algorithms to correctly identify products. Improvements like these should make the platform better at search and recommending products you didn’t know you wanted, or needed.

By way of example: “We know you’re having a baby and we show you some products near you,” says Liu, adding, “We know you searched for a crib.”

A smarter Marketplace could well draw people away from eBay, Craigslist and even Amazon, but so long as it keeps more eyes in the world of Facebook and on its ad network, it shouldn’t face the same fate as its predecessor any time soon.